1. Field of the Invention
The present invention relates to a packaging method, wherein a container having a container edge, and being filled with an article, has an upper opening face thereof covered by a film and a seal of an overlapped portion of the container edge and the film is effected.
2. Description of the Prior Art
Nowadays, there are provided in markets an extremely large number of articles that are packaged in containers. Like tofu or bean curd, packaged in the containers are many articles by covering an upper opening face of the container, filled with the articles, with a film and effecting a seal of an overlapped portion of a flange-like container edge and the film.
With such articles that are packaged by covering the upper opening face of the container and effecting a seal of the overlapped portion of the container edge and the film, the articles can be tightly sealed in the container so as to be kept clean. Liquid or juice also can be sealed, and shapes of the articles can be maintained by strength or rigidity of the container. Thus, such packaging is widely employed for many kinds of articles.
With resect to packaged articles of the above-mentioned kinds, in order for packaged liquid or juice not to leak from a container, a sealing ability between the container edge upper surface and the film must be ensured. But, on the other hand, when articles are to be removed from the container, it is desirable that the film on the container can be easily and smoothly peeled off without an excessive force being applied. Especially, like packaged tofu, when articles are sealed in a container together with liquid or juice, it is particularly desired that the container can be opened only with a smooth opening action so that the liquid or juice will not spill from the container when the film is being removed.
In order to ensure strength, sealing ability, and the like, simultaneously, the container and film, respectively, used for an article packaging are usually formed of a laminate in which a plurality of sheets or films are laminated. For example, the container is formed of a multi-layer structure in which a core portion made of polystyrene is sandwiched between upper and lower surfaces made of polypropylene, and the film is a laminate sheet made of nylon and polypropylene, so that the container and the film are joined together by a seal via polypropylene surfaces.
As the container and the film are so formed by the multi-layer sheet or multi-layer film, if they are joined together too strongly, a sealed portion is hardly peeled at a time of opening the container, so that an interlayer peeling may occur in the laminated film or container. Thus, the container cannot be smoothly opened and there often results a problem, such as jumping out or spilling of articles or liquid from the container. Or, otherwise there results a problem, such as tearing of the film in middle of the sealed portion between the container and the film because of difficulty in opening the container along the sealed portion, or breaking of the film on the container so as to cause a half-opening of the container. Hence, there has often been caused such a case in that a container has to be opened by using cutlery.
Also, in order to open the container, as the film on the container edge has only a small pulling tab at a corner portion of the container, it is not always easy to lift the small tab to peel the sealed portion and, moreover, a considerable force is required to pull the tab. Hence, at the very moment when the sealed portion begins to peel or when the film is suddenly broken, the container is necessarily moved, which often results in scattering liquid or juice from the container or upsetting the container.
It is therefore an object of the present invention to provide a packaging method, wherein a container having a container edge, and being filled with an article, has an upper opening face thereof covered by a film and a seal of an overlapped portion of the container edge and the film is effected, by which a sealing ability at a sealed portion is ensured and the film on a container edge upper surface can be smoothly and easily removed along the sealed portion without an excessive force being applied, so that a container package exhibiting an easy opening ability is obtained.